An induction coil of an induction heating apparatus is desirably supplied with a single-phase AC because when magnetic fluxes having different phases intersect with each other within the same magnetic circuit, the intersection causes a reduction in power factor and gives rise to non-uniformity in heat generation distribution.
On the other hand, a power source for the induction heating apparatus is typically a three-phase AC power source, and therefore in many cases, the single-phase AC is normally extracted from the three-phase AC.
Meanwhile, in a case of directly connecting induction coils of two induction heating apparatuses having the same specifications to U-V terminals and V-W terminals, the balance in phase currents among U-, V-, and W-phases becomes 1:√3:1 causing an unbalance by a factor of 1.732. This violates the regulation “an equipment unbalanced factor of 30% or less calculated from a single-phase connected load as a general rule” in “the limitation of unbalanced load, and special machinery and tools” in the extension regulations for low voltage and high voltage reception (JEAC: Japan Electric Association Code).
In order to prevent this violation, as disclosed in Patent Literature 1, there is a method that provides a Scott connection transformer between a three-phase power source and induction coils, and extracts single-phase AC outputs for the two circuits from the three-phase AC.
However, the Scott connection transformer is required, resulting in significant disadvantages in cost and space.